Superconducting joint for superconducting wires and coils

Abstract

The ends of a plurality of copper conductors bearing superconductive strands, for example of niobium-titanium, are treated with a liquid metal solvent to selectively remove the copper from the superconductive strands. The liberated strands of superconductor are then soldered with a superconducting solder. The joint is included in a coil which at superconducting temperatures induces a high magnetic field of 0.5 Tesla and above.

What is claimed and sought to be protected by Letters Patent of the United States is as follows: 
     
       1. A superconducting wire end adapted for being joined to other superconducting wire ends, said wire end having at least one hundred superconducting strands of less than 100 microns in diameter embedded in a matrix metal in one portion of said wire end,   said at least one hundred superconducting strands being liberated from and extending from said matrix in another portion of said wire end and being embedded in a superconducting solder metal, and   said superconducting wire end being capable of conducting at least 100,000 amperes of current at superconducting temperatures.   
     
     
       2. The wire end of claim 1 wherein the superconducting strand is niobium-titanium. 
     
     
       3. The wire end of claim 1 wherein a plurality of superconducting strands are embedded in said matrix metal as fine filaments. 
     
     
       4. The wire end of claim 3 wherein the superconducting strands are of niobium-titanium. 
     
     
       5. The wire end of claim 1 wherein the solder metal is lead-bismuth containing from 5 to 98% lead and the remainder bismuth. 
     
     
       6. The wire end of claim 1 wherein the solder metal is lead-bismuth containing from 30 to 56% bismuth and the remainder lead. 
     
     
       7. The wire end of claim 1 wherein the matrix metal is copper, the superconducting strand is niobium-titanium and the superconducting solder is lead-bismuth containing from 5 to 98% lead and the remainder bismuth. 
     
     
       8. A superconducting joint, said joint comprising a plurality of more than 100 strands of niobium-titanium conductor each being of less than 100 microns diameter and each 100 strands extending from each of two matrix metal wire ends, and   said strands of each matrix metal wire ends extending into a solder joint of superconducting solder metal, and   said joint being capable of conducting at least 100,000 amperes of current at superconducting temperatures.   
     
     
       9. The superconducting joint of claim 8 wherein the matrix metal is selected from the group consisting of copper and alloys of copper. 
     
     
       10. The superconducting joint of claim 8 in which the solder joint is a eutectic of lead and bismuth. 
     
     
       11. The superconducting joint of claim 8 wherein the superconducting solder metal is lead-bismuth containing from 5 to 98% lead and the remainder bismuth. 
     
     
       12. The superconducting joint of claim 8 wherein the superconducting metal is lead-bismuth containing from 30 to 56% bismuth and the remainder lead. 
     
     
       13. A superconducting coil, said coil comprising at least one winding of at least one hundred niobium-titanium superconductor strands of less than 100 microns diameter,   said at least one hundred superconductor strands being disposed in a metal matrix over most of their length,   the ends of said superconductor strands being liberated from and being free of said matrix metal,   said liberated ends being held together to form a strand-to-strand joint and being at least partially immersed in the same body of solidified lead-bismuth alloy, and   said coil being capable of conducting at least 100,000 amperes of current at superconducting temperatures.   
     
     
       14. The coil of claim 13 wherein the matrix metal is selected from the group consisting of copper and alloys of copper. 
     
     
       15. The coil of claim 13 wherein the lead-bismuth alloy is 5 to 98% lead and the remainder bismuth. 
     
     
       16. The coil of claim 13 wherein the lead-bismuth alloy is 44 to 70% lead and the remainder bismuth. 
     
     
       17. A superconducting coil comprising, a coil of at least one turn of superconducting wire,   said wire having multiple filaments of superconductor extending lengthwise through an elongated matrix metal,   said superconductor filaments being at least 100 in number and having diameters of less than 100 microns,   said coil having at least one wire to wire joint,   said joint containing filaments of said superconductor released from said matrix metal,   the released superconductor filaments of each wire being embedded in the same solidified body of superconducting solder metal, and   said superconducting coil being capable of conducting at least 100,000 amperes of current at superconducting temperatures.   
     
     
       18. A superconducting joint comprising a first set of at least 100 strands of less than 100 microns diameter of niobium-tantalum alloy, a second set of at least 100 strands of less than 100 microns diameter of niobium-tantalum alloy, strands of said first set being held in contiguous relation with strands of said second set to provide a superconducting path therebetween, strands of said sets being surface coated with at most a minor amount of tin and being frozen in a common body of lead-bismuth and said joint being capable of conducting a current of at least 100,000 amperes of current at superconducting temperatures.